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PLANT SCIENCE

PLANT SCIENCE

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PLANT SCIENCE

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  1. PLANT SCIENCE

  2. Plant Classification Examples 4 common plant divisions -Bryophyta: mosses and liverworts -Filicinophyta: ferns -Coniferophyta: coniferous plants -Angiospermatophyta: flowering plants

  3. A. Bryophytes=mosses, liverworts, hornworts 1. have no true roots, leaves or stems 2. have structures called rhizoids (rhizoids are root like structures that look like long hairs) rhizoids

  4. 3. mosses have simple leaves and stems 4. liverworts consist of a flattened thallus 5. a thallus is a plant body not divided into true roots, stems and leaves 6. bryophytes can grow up to 0.5 m 7. they do not produce flowers

  5. 8. bryophyte reproduction -can be sexual or asexual -often involves alteration of generations -spores are developed in capsules that are found at the end of stalks 9. bryophytes are often homosporous (the gametophytes contain male and female sex organs) 10.most common in damp habitats

  6. B. Filicinophytes (ferns) 1. have, roots, leaves and short non-woody stems 2. leaves are often curled up in buds and are often pinnate 3. pinnate=leaves divided into pairs

  7. 4. ferns are vascular plants -they have transport tissue called vascular bundles (xylem and phloem) 5. can grow up to 15m 6. filicinophyte reproduction- -spores are produced by sporangia, usually found on the underside of the leaves 7. ferns can be heterosporous or homosporous 8. ferns do not produce flowers

  8. C. Coniferophytes (conifers) 1. conifers are shrubs of trees with roots, leaves and woody stems 2. leaves are often narrow with thick, waxy cuticles 3. they are vascular plants 4. can grow up to 100m

  9. 5. reproduction- -seeds are produced -they develop in the ovules on the surface of the scales of the female cones -male cones produce pollen 6. coniferophyta are heterosporous 7. they do not produce flowers

  10. Immature female cone Mature female cone Male cone

  11. D. Angiospermatophyta-flowering plants 1. usually have true roots, leaves and stems 2. stems that develop into shrubs and trees are woody 3. can grow up to 100m

  12. 4. reproduction -seeds are produced -they develop in the ovary -ovaries are part of the flowers -fruits develop from ovaries to disperse the seeds 5. angiospermatophytes are heterosporous

  13. Xerophyte adaptations A. Xerophytes are plants adapted to dry environments --their adaptations allow them to obtain the maximum amount of water from their environment B. Xerophyte=‘dry plants’

  14. Xerophytes (cont) C. The adaptations 1. reduced leaves (reduced surface area) 2. thick waxy cuticle -reduces water loss 3. reduced number of stomata -reduces water loss, gas exchange and photosynthesis 4. Water storage tissue -helps in long dry periods

  15. Xerophyte adaptations (cont) 5. Stomata in pits and/or surrounded by hair -reduces air flow past pore -water that has diffused out will stay near -this reduces the concentration gradient and reduces the diffusion of water out of the plant

  16. Xerophyte adaptations (continued) 6. Vertical stems -allow absorption of light early and late in the day (not at midday when light is most intense) -reduces transpiration

  17. Xerophyte adaptations (cont.) 7. Wide-spreading shallow root network -allow immediate absorption of extensive amounts of water immediately after rain 8. CAM physiology -stomata open at night and stay closed during the day

  18. Hydrophyte Adaptations A. Hydrophyte= ‘water plant’ B. The adaptations 1. Air spaces -allow the plant to float on top of the water to absorb the most sunlight 2. Stomata found in upper epidermis (not in lower epidermis) -open to air

  19. Hydrophyte adaptations (continued) 3. Small amount of xylem in stems and leaves -xylem conducts water 4. Surrounded by water -roots serve mainly as anchorage (not water absorption

  20. Plant Leaf Structure and Function A. Leaf function=to produce food via photosynthesis (C3, C4, CAM) B. Leaves are adapted to their environments (C3, C4, CAM) C. Photosynthesis depends on gas exchange over a moist surface

  21. Upper epidermis Cuticle Palisade mesophyll Xylem Phloem Spongy mesophyll Lower epidermis Guard cell Stoma Plant Leaf Structure and Function D. Cross section of a leaf

  22. Plant Leaf Structure and Function E. Leaf anatomy 1. Upper epidermis-layer of cells covered by a thick waxy cuticle -prevents water loss from the upper surface 2. Palisade mesophyll-densely packed cylindrical cells -contain many chloroplasts -main photosynthetic tissue -positioned near top of leaf for maximum light absorption

  23. Plant Leaf Structure and Function E. Leaf anatomy 3. Xylem-vascular tissue responsible for water transport -replaces water lost during transpiration 4. Phloem-vascular tissue that transports minerals -transports photosynthetic products out of leaves 5. Spongy mesophyll-cells that provide a means for gas exchange -have fewer chloroplasts than the palisade mesophyll -found near stomata and lower epidermis

  24. Plant Leaf Structure and Function E. Leaf anatomy 6. Stoma (stomata =pl.) -pore that allows carbon dioxide to diffuse in and oxygen to diffuse out -also responsible for water loss 7. Guard cells-cells that open and close the stomata -control transpiration

  25. Root Anatomy (dicot) Special layer with root Hairs (protoderm) Epidermis Xylem Root hairs Phloem Pericycle Endodermis Cortex of parenchyma cells

  26. Cuticle (outside layer) Epidermis Stem anatomy (dicot) Xylem Pith of parenchyma cells Phloem Cortex of Parenchyma cells Cambium

  27. 13.2 Transport in Angiosperms Roots A. Plants take in water and minerals through their roots B. Roots have large surface area to allow for adequate uptake of water and minerals -they are branched and they have root hairs C. Function of the cortex=to facilitate water uptake D. Roots also act as anchorage to ground

  28. Roots and active transport A. Mineral concentrations are often higher in the root than in the soil B. This suggests active transport (going against the concentration gradient) C. Cortex cells can absorb ions that are dissolved in the water that is drawn by capillary action through the cortex cell walls

  29. Water Uptake By Roots A. Roots take in water via osmosis -Water in the soil contains a lower concentration of solutes than the cytoplasm of root cells -This causes water to diffuse in to the roots

  30. Water Uptake by Roots Root cell Soil High solute Low solute H2O H2O **Water diffuses (osmosis) to an area of high solute concentration to reach equilibrium between the roots and the soil **Minerals are taken in via active transport because the roots have higher solute concentration than the soil

  31. Water Uptake By Roots (continued) B. Most absorbed water is eventually drawn to the rest of the plant because of transpiration -as water leaves the leaves it must be replaced C. To get water from the root hairs to the xylem, there are three possible methods -apoplast, symplast or vacuolar pathways

  32. Water Uptake By Roots (continued) D. Apoplast pathway -water does not enter the root cells -it travels by capillary action through the cell walls of the cortex until it reaches the endodermis -cells of the endodermis have Casparian strips around them that are impermeable to water -to pass through the endodermis the water must follow the symplast pathway (the apoplast pathway stops at the endodermis)

  33. Water Uptake By Roots (continued) E. Casparian Strips -found in endodermis -thought to be a protective measure -prevent water from seeping between cells -forces water to enter the endodermis before passing to the vascular tissue -forces water to go through cell walls (not between them

  34. Water flow with Casparian strips Cell wall Casparian strip Cell membrane Vacuole Water flow (cannot flow between cells when Casparian strips are present) Water flow without Casparian strips Cell wall Cell membrane Vacuole Water flow

  35. Water Uptake By Roots (continued) F. Symplast Pathway -water enters the cytoplasm of the cells, but not the vacuole -water passes from cell to cell via the plasmodesmata (connections of cytoplasm between cells) -the water eventually enters the xylem

  36. Movement Through Roots

  37. Water Uptake By Roots (continued) G. Vacuolar Pathway -water enters the cells and moves to the vacuole -when necessary the water will travel through the cytoplasm and cell wall to the vacuole of the next cell

  38. Assignment: Make a chart to compare apoplast, symplast and vacuolar pathways

  39. The Xylem A. Function-to transport water and dissolved minerals from the roots to other parts of the plant B. Mature xylem cells are dead C. Made of two components 1. tracheids 2. xylem vessels

  40. The Xylem (continued) D. Tracheids -narrow cells, arranged in columns -overlap at tapered ends -function as support -overlapping ends have pits that allow water to move rapidly between cells -all plants have tracheids -not as efficient as xylem vessels

  41. The Xylem (continued) E. Xylem vessels -most water travels through vessels -composed of columns of cells -when the cells die the walls between them disappear partly or completely (leads to more efficient transport) -diameter is wider than tracheid diameter -side walls are reinforced with lignin (this helps with structural support)

  42. Xylem vessel Tracheid

  43. Water Transport Through Plant Tissue A. Transpiration=loss of water vapor from leaves and stems B. Transpiration causes water flow from roots, through stems and to the leaves C. Transpiration stream = describes the transpiration flow through the plant D. The process begins with evaporation of water from the leaves (through the spongy mesophyll)

  44. Water Transport Through Plant Tissue (continued) E. Evaporated water is replaced with more water from the xylem F. Capillary action allows the water to move from the xylem to the spongy mesophyll G. The capillary action creates transpiration pull -transpiration pull= low pressure or suction within the xylem H. Water molecules have strong cohesion forces

  45. Water Transport Through Plant Tissue (continued) I. As water moves out of the vessel, other molecules will want to replace it J. All water will move up a little (toward the leaves), at the other end of the plant (the roots) water will move from the soil to the plant

  46. Water Cohesion A. Water molecules are attracted to each other B. These are intermolecular forces C. This is created by hydrogen bonding The whole point: EVAPORATION CAUSES TRANSPIRATION PULL. THIS PULLS WATER INTO THE ROOTS AND TO THE REST OF THE PLANT BECAUSE OF THE STRONG COHESION OF WATER MOLECULES.

  47. Phloem A. Primary function= translocation B. Translocation-movement of substances from one part of a plant to another in the phloem C. Sugars, amino acids and other organic compounds produced by photosynthesis are transported away from the leaf -materials sprayed on the plant can also be transported from the leaves via the phloem

  48. Phloem D. Found in all leaf veins E. Materials can be transported in both directions **Remember xylem only transports one way (up) Ex: In summer trees transport sugars from leaves to roots -In spring transport sugar from roots (where it is stored) to the new branches